Transcutaneous electrical nerve stimulation (TENS) is a type of therapy used
primarily for analgesia, but also presents changes in the cardiovascular system
responses; its effects are dependent upon application parameters. Alterations to the
cardiovascular system suggest that TENS may modify venous vascular response. The
objective of this study was to evaluate the effects of TENS at different frequencies
(10 and 100 Hz) on venous vascular reactivity in healthy subjects. Twenty-nine
healthy male volunteers were randomized into three groups: placebo (n=10),
low-frequency TENS (10 Hz, n=9) and high-frequency TENS (100 Hz, n=10). TENS was
applied for 30 min in the nervous plexus trajectory from the superior member (from
cervical to dorsal region of the fist) at low (10 Hz/200 μs) and high frequency (100
Hz/200 μs) with its intensity adjusted below the motor threshold and intensified
every 5 min, intending to avoid accommodation. Venous vascular reactivity in response
to phenylephrine, acetylcholine (endothelium-dependent) and sodium nitroprusside
(endothelium-independent) was assessed by the dorsal hand vein technique. The
phenylephrine effective dose to achieve 70% vasoconstriction was reduced 53%
(P<0.01) using low-frequency TENS (10 Hz), while in high-frequency stimulation
(100 Hz), a 47% increased dose was needed (P<0.01). The endothelium-dependent
(acetylcholine) and independent (sodium nitroprusside) responses were not modified by
TENS, which modifies venous responsiveness, and increases the low-frequency
sensitivity of α1-adrenergic receptors and shows high-frequency opposite effects.
These changes represent an important vascular effect caused by TENS with implications
for hemodynamics, inflammation and analgesia.
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